Hollow Stem Augers Overview

Hollow Stem Augers Overview

Overview

Hollow Stem Augers are used extensively for soil sampling and ground water monitoring in industrial and commercial installations around the world. Unlike Solid Augers, drill rods can pass through the center of Hollow Stem Augers to take undisturbed soil samples for analysis or to install pipe for ground water monitoring. For ground water sampling, Hollow Stem Auger walls can be slotted, allowing water to pass through the center. Other applications demand that Hollow Stem Augers be used as temporary casings to prevent borehole walls from sloughing or caving in. Whatever the application, Mills Machine Company stands ready to meet our customers' needs. Mills Machine Hollow Stem Augers are fully reversible through the use of drive keys that transfer the torque directly from auger to auger. The auger cutterhead has a slightly larger O.D. than the auger flighting to increase the life of the flighting edges and improve soil removal. The cutterhead and pilot bit break up and drill the material, while the auger flighting acts as a screw conveyor to move dirt from the bottom of the hole. The flighting pitch determines the efficiency and lifting speed of the auger.

Mills Machine Hollow Stem Auger Specifications

Mills Machine Co. has been manufacturing Hollow Stem Augers for over 20 years. Our augers feature either standard duty or heavy duty tapered tool joints, single or double lock bolt connections, and a double key or triple key drive system. Mills Machine Hollow Stem Auger tubing and flighting are made from premium carbon steel, with 4142 heat-treated alloy steel tool joints. The flighting has continuous hardfacing, for durability, and is thicker than most of our competitors', with 3/8" thick being the standard for our stocked augers. Our stocked augers are 5 feet (1.5 meters) long and range from 2 1/4" I.D. to 12 1/4" I.D. (5 5/8" O.D. to 17" O.D.). Mills Machine Standard Duty Hollow Stem Augers are designed for use in shallow hole applications and are recommended for depths up to seventy feet. For deeper drilling, Mills Machine Heavy Duty Hollow Stem Augers should be used. Mills Machine Heavy Duty Hollow Stem Auger feature heavier, tapered tool joints and larger nuts, bolts, and drive keys. They are designed for use in depths exceeding 70 feet. Variations in auger specifications are common. Mills Machine stands ready to meet those differences with a strong history of custom design and development that continues to establish us as a leader in the field. We carry an inventory of all the standard components and are ready to meet your special needs with a rapid design and delivery time.

Drilling Operation

For normal hole advancement, a pilot bit is inserted through the cutterhead to drill the center of the hole. The drill rod is bolted to the inside of the drive cap with a rod-to-cap adapter so that the pilot bit can turn in tandem with the augers. Drill rods must be added each time an auger is added. In soft formations (dirt and sand), a tapered plug may be inserted into the end of the cutterhead to prevent material from going up inside the augers and to eliminate the use of drill rod. When the hole is completed, the plug may be knocked out the bottom of the auger string. The next step is to insert the monitoring screen and casing, which is then grouted into place to prevent contamination from the top of the hole.

HollowStemAugerConstruction

Hollow Stem Auger Construction

The complete Hollow Stem Auger string is shown here. The numbers correspond with the numbers on each of the following pages of our stocked auger sizes. Our stocked hollow stem augers are 5 feet (1.5 meters) long and range from 2 1/4" I.D. to 12 1/4" I.D. (5 5/8" O.D. to 17" O.D.).

  1. The Hollow Stem Auger itself is made up of a premium carbon steel tube, 3/8" thick hard-faced carbon steel flighting, and 4142 heat-treated alloy steel tool joints. Mills Machine Standard Duty Hollow Stem Augers are designed for use in shallow hole applications up to 70 feet. For deeper drilling, Mills Machine Heavy Duty Hollow Stem Augers should be used, featuring heavier, tapered tool joints, larger bushing nuts, larger lock bolts, and larger drive keys, for added strength.
  2. The Auger Drive Cap connects the auger string to the rig's drive. It features a hex pin connection to match the rig's drive (1 5/8", 2", etc.) and box connection to match your auger string.
  3. The Nut & Bolt for the Rod-to-Cap Adapter holds the Rod-to-Cap Adapter in place inside of the drive cap.
  4. The Auger Pilot Bit Connector connects the internal drill rod to the auger pilot bit and also centers the pilot bit.
  5. The Rod-to-Cap-Adapter connects the drive cap to the drill rod string, enabling the drill rods and the pilot bit to turn in tandem with the auger string.
  6. Auger Drill Rod
  7. Auger Lock Bolts
  8. Auger Bushing Nuts
  9. Auger Drive Keys
  10. Auger Cutterheads cut the O.D. of the hole for the auger. Mills Machine cutterheads come in 6 different variations: Blade, Spade, Blade/Bullet, Spade/Bullet, Bullet, and 5-T. Read more about these in Section 2: Hollow Stem Auger Components, Auger Cutterheads.
  11. Auger Pilot Bits are connected to the drill rod with the Auger Pilot Bit Connecter and fit into the center of the Auger Cutterhead to drill the center of the hole. Mills Machine pilot bits come in either Apex or Bullet types. Read more about these in Section 2: Hollow Stem Auger Components, Auger Pilot Bits.